Abstract : The design of a dual polarisation high resolution synthetic aperture space based radar is discussed which incorporates features which allow an adaptable operation mode to be utilised for ocean or land observation. The requirements for wide coverage for ocean observation of shipping at lower spatial resolution and the requirements for smaller area coverage at higher resolution of specific target areas in one instrument presents the designer with a significant challenge. The described instrument incorporate dual polarisation receive features with selectable polarisation transmit. Wide coverage transmit beams are utilised with a narrow steerable receive beam which follows the time dependent return signals in angle. The transmission of raw measurements to ground based facilities is impractical for high resolution and the instrument must perform on board much of the necessary data analysis. Such an operation is now practical, if costly in power, and allows for ocean surveillance the transmission of the position of possible targets with a future extension to more 'intelligent' analysis.